package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;

import java.lang.reflect.*;
import java.util.List;

public class DefaultSqlSession implements SqlSession {

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementid, Object... params) throws Exception {

        //将要去完成对simpleExecutor里的query方法的调用
        simpleExecutor simpleExecutor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);

        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementid, Object... params) throws Exception {
        List<Object> objects = selectList(statementid, params);
        if(objects.size()==1){
            return (T) objects.get(0);
        }else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }


    }

    @Override
    public <T> T insert(String statementid, Object... params) throws Exception {
        //将要去完成对simpleExecutor里的insert方法的调用
        simpleExecutor simpleExecutor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        Integer result = simpleExecutor.insert(configuration, mappedStatement, params);
        return (T) result;
    }

    @Override
    public <T> T delete(String statementid, Object... params) throws Exception {
        simpleExecutor simpleExecutor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        Integer result = simpleExecutor.delete(configuration, mappedStatement, params);
        return (T) result;
    }

    @Override
    public <T> T update(String statementid, Object... params) throws Exception {
        simpleExecutor simpleExecutor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        Integer result = simpleExecutor.update(configuration, mappedStatement, params);
        return (T) result;
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        // 使用JDK动态代理来为Dao接口生成代理对象，并返回d

        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
                // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
                // 方法名：findAll
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();

                String statementId = className+"."+methodName;
//                Map<String, MappedStatement> mappedStatementMap =
                //获取mapper xml的对象
                MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);

                // 准备参数2：params:args
                // 判断是否进行了 泛型类型参数化
//                if(genericReturnType instanceof ParameterizedType){
//                    List<Object> objects = selectList(statementId, args);
//                    return objects;
//                }
                //使用sqlType 判断curd类型
                String sqlType = mappedStatement.getSqlType();
                //TODO 判断增加删除 修改
                switch (sqlType) {
                    case "SELECT":
                        // 获取被调用方法的返回值类型
                        Type genericReturnType = method.getGenericReturnType();
                        //判断是否实现泛型类型参数化
                        if (genericReturnType instanceof ParameterizedType) {
                            List<Object> objects = selectList(statementId, args);
                            return objects;
                        }
                        return selectOne(statementId, args);
                    case "INSERT":
                        return insert(statementId, args);
                    case "UPDATE":
                        return update(statementId,args);
                    case "DELETE":
                        return delete(statementId, args);
                    default:
                        throw new RuntimeException("未知sql 类型..");
                }
            }
        });
        return (T) proxyInstance;
    }


}
